(a) Field of the Invention
The present invention relates to an optical microscope, and more particularly it pertains to a surgical microscope.
(b) Description of the Prior Art
In surgical operations conducted by utilizing a surgical microscope, it is being demanded that two observers, i.e. a surgical operator and his assistant who is positioned in a direction forming substantially right angles relative to the operator about the vertical central axial line of the microscope body, are able to observe the region of operation in a same state.
As the means for materializing such a demand, there is the device of the type disclosed in, for example, Japanese Patent Publication No. Sho 55-10174. This will be described hereunder by referring to FIGS. 1 and 2.
A specimen not shown is located at a position on the downward extension of a pair of operator's observational optical axes "a". In connection therewith, there are disposed on said optical axes "a" an objective lens 1, auxiliary lenses L.sub.a, L.sub.b, and further, light beam splitting prisms P.sub.1, P.sub.1 ', respectively. In the directions of straightforward transmission through these light beam splitting prisms P.sub.1, P.sub.1 ', there extend the operator's observational optical axes "a", and on their extensions, there is further disposed an binocular observational optical system not shown. The surgical operator (hereinafter to be referred to simply as "operator") makes an observation by utilizing this observational optical system. On the other hand, in the directions in which the light beams are so split and deflected by the light beam splitting prisms P.sub.1, P.sub.1, there extend a pair of assistant's observational optical axes "b" as shown by chain lines. On said optical axes "b" of the assistant, there is provided an assistant's binocular observational optical system which comprises prisms P.sub.3, P.sub.3 ', P.sub.4, P.sub.4 ', and ocular lenses 2, 2'. Accordingly, by utilizing the operator's observational light beams which have been so split by the light beam splitting means P.sub.1, P.sub.1 ', the assistant is enabled to observe the same observational images I.sub.n, I.sub.n ' as for the operator.
However, with the device of the above-mentioned type, while both the operator and the assistant are capable of making an observation of the region for surgery with a same magnification and in coaxial relationship, there has been the problem from the aspect of stereoscopic viewing that, while the operator is able to obtain a stereoscopic view, his assistant is unable to obtain a stereoscopic view. This is because of the reasons that, since the light bundles coming from the operator side are led as they are to the assistant side, the bilateral view field images on the assistant's binocular observational optical system are exactly those bilateral view field images as viewed at the operator's position, so that these images will serve as the vertical view field images for the assistant, with the result that there is produced, for the assistant, no bilateral parallax necessary for his stereoscopic viewing, but instead a vertical parallax.